1. Field of the Invention
The present invention relates to a lens shape measuring apparatus for measuring an edge thickness of an unprocessed eyeglass lens in a position corresponding to lens shape data.
2. Description of the Prior Art
Conventionally, in a lens grinding apparatus, to match axial degrees of an optical center position, an astigmatic axis and the like with one another when a lens to be processed is attached, an adsorption cup, a tape cup using or a double-sided tape or the like has been used.
Such a tape has been used in order to attach and process the lens to be processed in an accurate position. A size of the tape must be as small as possible, because a lens shape (lens frame shape of an eyeglass frame) having a small radius vector can be formed in processing.
However, to hold the lens to be processed against processing resistance of a grinding wheel, it is advantageous to increase not only a force for clamping the lens to be processed but also a diameter of the adsorption cup for fixing the lens to be processed.
Therefore, for outer diameters of a lens fixing jig such as the adsorption cup or the tape cup, a cup receiver installed therein, and a lens pressing portion, large outer diameters (generally about 25 mm) for obtaining a sufficient champing foe with respect to a normal frame size, and small outer diameters (about 16 mm to 20 mm) for dealing with a normally possible smallest frame size, have bee used.
When a fixing jig such as an adsorption cup of a small outer diameter is used, for example as disclosed in Japanese Patent Laid-Open Nos. 1990-190249 (EP 379427 B1), and 2000-317796 (EP1050272 A1), in the recent lens grinding apparatus, since a lens shape such as a frame shape, and a processing size can be identified beforehand, an operator can be advised to use a small fixing jig by displaying a message on a liquid crystal screen or by voice or the like. However, in actual processing, the apparatus itself cannot detect the attachment of the small fixing jig. Consequently, an accident of grinding the lens fixing jig together with the lens to be processed occurred in processing.
Furthermore, in the recent lens grinding apparatus, a position of a V groove formed in a circumferential edge of the eyeglass lens is generally controlled by abutting a measuring element on front and rear refracting surfaces of the eyeglass lens, and tracing the refracting surfaces along a lens shape (frame shape) to measure an edge thickness and a shape of the eyeglass lens, before the eyeglass lens is ground. However, in such measuring of the shape of the eyeglass lens, for example if a large holder was used for the eyeglass lens to be finished in a lens shape (frame shape) of a small outer diameter such as a crab-eye frame, the measuring element measured an outer diameter portion of the lens fixing jig, causing a measuring error and, in some cages, an excessive force was applied to break the measuring element.
A first object of the present invention is to solve the above-described problem and provide a lens shape measuring apparatus capable of identifying a size of an outer-diameter shape of a lens fixing jig by using a measuring element also used for measuring a lens shape.
A second object of the present invention is to solve the problem and provide a lens shape measuring apparatus capable of identifying a size of an outer-diameter shape of a lens fixing jig in a direction roughly parallel to a lens rotation shaft by using a measuring element also used fox measuring a lens shape.
A third object of the present invention is to solve the above described problem and provide a lens shape measuring apparatus capable of identifying a size of an outer diameter shape of a lens fixing jig in a rotational axial direction of a measuring element roughly parallel to a lens rotation shaft by using the measuring element also used for measuring a lens shape.
In order to achieve the first object, a lens shape measuring apparatus according to a first aspect of the present invention comprises: a lens fixing jig installed in a lens to be processed to clamp the lens; a lens rotation shaft for clamping and rotating the lens to be processed; a measuring element abutted on a refracting surface of the lens clamped by the lens rotation shaft; a measuring unit for measuring a moving distance of the measuring element; and arithmetic control means for identifying a shape of the lens fixing jig based an the moving distance of the measuring element measured by the measuring unit.
In order to achieve the second object, a lens shape measuring apparatus according to a second aspect of the present invention comprises: a lens fixing jig installed in a lens to be processed to clamp the lens; a lens rotation shaft for clamping and rotating the lens to be processed; a measuring element abutted on a refracting surface of the lens clamped by the lens rotation shaft; a measuring unit for measuring a moving distance of the measuring element in a direction roughly parallel to the lens rotation shaft; and arithmetic control means for moving a tip of the measuring element relatively in the direction roughly parallel to the lens rotation shaft; measuring a distance from a measuring reference position of the measuring element to an abutting position of the same by the measuring unit, and identifying a shape of the lens fixing jig based on a result of the measurement.
In order to achieve the third object, a lens shape measuring apparatus according to a third aspect of the present invention comprises: a lens fling jig installed in a lens to be processed to clamp the lens; a lens rotation shaft for clamping and rotating the lens to be processed; a measuring element abutted on a refracting surface of the lens clamped by the lens rotation shaft; measuring element rotating means for controlling rotation of the measuring element around a rotation shaft roughly parallel to the lens rotation shaft; a measuring unit for measuring a moving distance of the measuring element in a direction roughly parallel to the lens rotation shaft; and arithmetic control means for rotating a tip of the measuring element around the lens rotation shaft, and identifying a shape of the lens fixing jig based on a distance of the abutted position of the tip of the measuring element from a measuring element reference position.